Spitfire hum problem

[EtherealWidow]

It's definitely something happening in the first stage. Removed all the tubes except V1, dimed the tone control and turned the master up halfway and took readings with the DMM and got some loud pops, but no oscillations.

Also loosened the input jacks and when I moved them around I can either get some playability with the master low enough or total, screaming oscillation. The grid leak is soldered directly onto the jack, but not the stoppers. Those are mounted on the board as per the layout.

[EtherealWidow]

Alright. So with the tone knob down I can get a little more out of the master volume before it starts getting unstable. I also unscrewed the OT and rotated it and was able to get a just little more out of it. The OT is right next to V1 btw. I know this might seem like a "duh" to some, but on my modded (higher gain) HO it worked just fine. Guess not this time. I'm thinking about taking your advice and just completely rewiring the whole thing on account of the oscillations and short circuits I've had. Not to mention the super UGLY forked turrets with big solder blobs. Might just go PTP. What's your input?

[EtherealWidow]

I think this chassis is such a tight squeeze that it's really all or nothing. I think I'm gonna salvage the small components I can, draw the circuit out, and just order up some terminal strips.

[EtherealWidow]

Finally got this thing up and running. PTP was a lot more enjoyable than using a board, although it's also a lot uglier until i get better with my technique. Sounds great, but this thing is a CLEAN MACHINE. I know that it's known for having a lot of headroom because if the high supply voltage for each stage, but honestly with the gain and master dimed all I get is some jangle. Also, there's not much difference between the hi and lo inputs, nor does the tone knob make as big a difference as I feel it should, and it seems quieter than the Hi Octane I built with a single '84. Funny know if this is normal as I don't have an actual Spitfire to use as a reference.

[EtherealWidow]

I know that it would seem quieter due to it being clean, but I can have a conversation over it when it's full blast. The PI is properly grounded at both inputs.

And the tone knob is noticeable, just not as much as, say, the one found on the guitar.

And the full output jangle is with humbuckers.

[EtherealWidow]

Turns out it was yet another short circuit. Simply two resistor leads touching that had no business touching each other. Terribly sorry to waste your time. Amp sounds much more like I expected it to. Good bit of grind and more on par with what I expect a cranked 15W to sound like. Tone control works better now and the Hi and Lo inputs are actually functioning as they should.